[pve-devel] [RFC cluster 3/6] cluster create: use new corosync-link format for totem interfaces

[Wolfgang Bumiller]

On Wed, May 29, 2019 at 11:16:50AM +0200, Thomas Lamprecht wrote:
> On 5/29/19 10:45 AM, Fabian Grünbichler wrote:
> > On Tue, May 28, 2019 at 06:33:10PM +0200, Thomas Lamprecht wrote:
> >> @@ -218,7 +220,7 @@ sub create_conf {
> >>  	    ip_version => $use_ipv6 ? 'ipv6' : 'ipv4',
> > 
> > and instead either set ip_version to 'ipv4-6' (ask DNS, prefer IPv4) or
> > leave it out altogether (which defaults to 'ipv6-4' for knet).
> 
> OK, we still fallback to the IP resolved by node's hostname, so this
> works for default cases too, I mean internally they hopefully don't
> try to do a DNS lookup if they get an IP? man page does not specifies
> the exact behavior, but it really should do so..
> 
> @Wolfgang, any issues you can think of with IPv6-4, i.e., prefer first
> IPv6 addr found over IPv4 addr found?

IMO this is a wrong design on corosync side? Why is there no "just use
the first address from getaddrinfo()?" or "just try them in order",
those are the only 2 correct behaviors IMO, anything else just causes
weird edge cases.

Systems can can already define a preference used by getaddrinfo()
(/etc/gai.conf), and and it even has a flag (AI_ADDRCONFIG) to assert
that the returned address is only used if a local address of the same
family actually exists on the system...

It's weird.